JPH1048975A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a good image by discriminating the sort of a transfer member securely, and converting the fixing condition according to the respective sort of the transfer member. SOLUTION: It is discriminated whether a transfer material 4 is a light permeable sheet or not by a permeating type optical sensor 9, and it is discriminated whether the transfer material 4 is a glossy paper or not by a reflection type optical sensor 8. When the transfer material 4 is a light permeable sheet, and when the transfer material 4 is a glossy paper, it is controlled to make the fixing condition of a fixing device optimum corresponding to the respective condition, by using a computer 11. That is, when the transfer material 4 is a light permeable sheet, the conveying speed of the transfer member 4 is made slower then the conveying speed at the fixing time of the glossy paper, by regulating by the computer 11. And when the transfer material 4 is a glossy paper, the conveying speed of the transfer material 4 is made slower than the conveying speed at the fixing time of a normal paper, by regulating by the computer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus in which fixing conditions are set according to the type of a transfer material.

[0002]

2. Description of the Related Art As a color image forming apparatus for forming a color image on a transfer material by superposing toner images of a plurality of colors, an electrostatic latent image is formed on a photoreceptor, and the latent image is sequentially developed with a toner agent. And transfer it to the transfer material each time,
There are a method of superimposing a plurality of color toner images on a transfer material, and a method of superposing a plurality of toner images on a photoreceptor or an intermediate transfer member and transferring these onto a transfer material at once.

[0003] Among them, the former method is a German DE26.
No. 07727, Japanese Patent Application Laid-Open No. 50-50935, and the like, which are practically used. on the other hand,
The latter method has problems such as color mixing at the time of development and image quality deterioration at the time of retransfer, but has advantages such as simple structure.
This technology is currently attracting attention.

[0004] In either system, finally, as shown in FIG. 8, a plurality of color toner images T formed on the transfer material 4 are heat-fixed by a fixing means, so that the toner images of each color are formed. By mixing, a full-color image can be obtained.

Referring to FIG. 8, an example of a fixing device using a heat roller system will be described.

In FIG. 1, reference numeral 1 denotes a toner T on a transfer material 4.
Is a fixing roller for melting and fixing by heating and pressing, and 2 is a pressing roller for pressing. Usually, the fixing roller 1 is often heated from the inner surface using a heater 26 such as a halogen lamp. Therefore, the fixing roller 1
In general, the surface temperature is monitored by a temperature detecting element 25 such as a thermistor, and the heater 26 is turned on and off to adjust the temperature. The color toner image T generally uses four color toners of yellow, cyan, magenta, and black.

When fixing the color toner image T, unlike the case of normal black and white printing, not only the fixing property but also the melt-mixing property of each color is an important factor for proper color reproduction. Therefore, the color toner image T is
In addition to chromatic colors as well as black toner, the formulation of the binder and the like is devised so that the melting point is slightly lower than that of the black toner of a generally used black-and-white copying machine. For example, a method of shifting the molecular weight of a material such as a styrene-acrylic resin or polyester used as a binder resin to a lower molecular weight, or a method of blending a low melting point wax as a release agent is generally used.

Therefore, the fixing roller 1 is likely to be offset more easily than the case where fixing is performed with black toner as used in a normal black-and-white copying machine or printer. As one method for preventing offset, as shown in FIG. 8, an oil applying device 22 having a supply roller 24 and an application roller 23, and a coating / cleaning web 21 are used to release a release agent oil such as silicone oil. 27 is applied to the surface of the fixing roller 1.

At this time, the low melting point toner is melt-fixed at a fixing temperature slightly higher than the fixable temperature so that the toners of the respective colors are sufficiently melted and mixed to improve the above-described color mixing property. As shown in FIG. 9, the surface of the core 1 is made of a silicone rubber 29 (HTV, LTV, etc.) having excellent elasticity and strength.
In many cases, the surface is coated with a low-hardness silicone rubber 30 (LTV, etc.) having excellent releasability, so that the toner is wrapped and the heat transfer efficiency is improved. .

The pressure roller 2 also has a surface of a core metal 31 made of aluminum or the like which is made of silicone rubber 32 having an appropriate hardness.
(HTV, LTV, etc.), and the surface is coated with a thin layer of fluororesin 33, or, similarly to the fixing roller 1, covered with a low-hardness LTV.

Of course, the configuration may vary depending on the type of the release agent oil 27. For example, when a methylphenyl-based silicone oil is used as the release agent oil 27, the above configuration can be used. However, when dimethyl silicone oil is used, the gap between the silicone rubbers 29 and 30 of the fixing roller 1 is Further, a blocking layer for preventing lubrication may be provided.

As other methods for preventing the offset, a method in which a belt-like fixing means is used in place of the fixing roller 1 to heat and fix the transfer material and then cool and separate the transfer material, or a method in which the toner T is superposed There is a method in which oil is not required to be applied to the fixing roller 1 by forming by a legal method and enclosing a wax or an oil component in the component.

[0013]

In the above-described conventional color image forming apparatus, the amount of toner is larger than that of a monochrome apparatus (because four colors are superimposed). Since the toner cannot be obtained, the fixing device applies sufficient heat to melt the toner.
Image). However,
On the other hand, when creating a color business application document, the user may not like such a high gloss, and in recent years, an image having a low gloss is output by slightly lowering the meltability. .

One of the difficult techniques when fixing a color image
One is the case where an image is formed on an overhead projector paper (hereinafter, referred to as “OHT”) which is a light-transmitting sheet. In such a case, if the toner is not sufficiently melted more than plain paper, color appears at first glance. Even if it looks like it is projected, it becomes a black image when projected with light. Therefore, various measures have been taken, such as reducing the speed of the fixing device during OHT fixing and providing a special resin layer on the OHT sheet surface.

On the other hand, in contrast to the above-mentioned low gloss reduction, a user who has high image quality such as a photographic image may prefer a sufficiently fused high gloss image. In such a case, as in the case of the OHT, some measures such as reducing the speed of the fixing device, increasing the fixing temperature, and using coated paper or plastic special paper having a special gloss are taken. ing.

[0016] However, in order to sufficiently transmit the OHT and to make the image of the high gloss paper (high gloss paper) truly high gloss, while making the image of low gloss in ordinary printing, the fixing device side is required. Fixing conditions must be significantly changed in each case. As an example, if the fixing speed is reduced, the amount of fixing heat can be increased in proportion to the fixing speed. In this case, for example, in the OHT, for example, about 1/3 or less of the high gloss paper is compared with the ordinary low gloss state. But almost 1 /
In some cases, the speed must be reduced to two or less. As described above, when the fixing speed is greatly reduced and the fixing heat amount is increased, in a case where plain paper is excessively passed, a remarkable hot offset occurs, and the fixing roller 1 and the temperature detecting element in contact with the fixing roller 1 are caused. Inconveniences such as the toner 25 being contaminated by the toner and the transfer paper itself wrapping around the fixing roller 1 are caused.

On the other hand, in order to avoid these problems, it is ideal that the type of transfer material, such as plain paper, OHT, or high gloss paper, is automatically detected by the printer. Or, a transmission type optical sensor cannot accurately determine the type of the transfer material. That is, the reflection type optical sensors are roughly classified into specular reflection type and diffuse reflection type, but the former regular reflection type sensor has difficulty in distinguishing OHT from high gloss paper, and the latter diffuse reflection type sensor has high gloss. It is difficult to distinguish between paper and plain paper. Moreover, in both cases, if the position accuracy of the measured object (transfer material) is poor, there is a problem that sufficient detection accuracy cannot be obtained. Further, the transmission type optical sensor can stably distinguish OHT from paper regardless of the position of the measured object, but cannot distinguish plain paper from high gloss paper.

Further, as described above, particularly when OHT is detected, it is necessary to greatly reduce the fixing speed. However, if the OHT detection timing is too late, there is a problem that sufficient time cannot be taken to reduce the speed. There is also. For example, in a small machine in which the interval between transfer and fixing is shorter than the maximum paper size, it is necessary to reduce the speed of fixing and transfer at the same time.To do so, the speed must be reduced before the transfer material enters the transfer position. There are design difficulties, such as the need to perform a reduction, and reflective optical sensors with unstable detection are also disadvantageous in this regard.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to reliably identify the type of transfer material, change the fixing conditions according to each type, and obtain a good image. It is an object to provide an image forming apparatus as described above.

[0020]

According to a first aspect of the present invention, there is provided an image forming apparatus including a fixing unit for fixing a toner image transferred onto a transfer material. Is disposed at a predetermined position on the upstream side of the transfer path of the transfer material from the transfer position of the toner image to the transfer material,
A transmissive optical sensor that identifies whether the transfer material is a light transmissive sheet, and is disposed on the downstream side of the transfer path of the transfer material from the transmissive optical sensor and upstream of the transfer position,
A reflective optical sensor that identifies whether the transfer material is glossy paper; and, if the transfer material is not a light-transmitting sheet, identifies whether the transfer material is glossy paper by the reflective optical sensor. And a control unit for setting a fixing condition of the fixing unit for fixing the toner image on the transfer material based on the identification result.

According to the second aspect of the present invention, the reflection-type optical sensor is disposed downstream of the transmission-type optical sensor on the transfer material conveying path and near the pair of registration rollers upstream of the transfer position. Have been.

According to the third aspect of the present invention, the reflection type optical sensor is a regular reflection type optical sensor.

According to the fourth aspect of the present invention, the control means sets the transfer speed of the transfer material as the fixing condition.

According to the fifth aspect of the present invention, the control unit sets a fixing temperature of the fixing unit as a fixing condition.

[Operation] Based on the above configuration, according to the present invention, whether or not the transfer material is a light-transmitting sheet is identified by the transmission type optical sensor, and the transfer material is glossy by the reflection type optical sensor. Identify whether it is paper. And
When the transfer material is a light transmissive sheet and when the transfer material is glossy paper, the control unit controls the fixing condition of the fixing unit to be optimal for each case. That is, when the transfer material is a light-transmitting sheet, the fixing conditions, for example, the transfer speed of the transfer material are adjusted to be lower than the transfer speed at the time of fixing glossy paper. When the transfer material is glossy paper, the fixing conditions, for example, the transfer speed of the transfer material are adjusted to be lower than the transfer speed at the time of fixing the plain paper.

According to another aspect of the present invention, the accuracy of detecting glossy paper and plain paper is improved by arranging the reflection type optical sensor near the pair of registration rollers.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention. In FIG. 1, reference numeral 3 denotes a fixing device including a fixing roller 1 and a pressure roller 2. The image carrier uses, for example, an intermediate transfer belt 5 as an intermediate transfer member. The toner image T is laminated on the intermediate transfer belt 5 in the order of magenta (M), cyan (C), yellow (Y), and black (K) (the outermost layer is black). The transfer roller 6 and the opposing roller 7 collectively transfer the toner onto the transfer paper 4 as a transfer material.
Magenta flips to the top layer). Here, as the intermediate transfer belt 5, a known polyethylene terephthalate, polyvinylidene fluoride, urethane, or other resin belt, or an ethylene propylene rubber, nitrile rubber, urethane, chloroprene rubber, or another rubber belt can be used. Further, the toner is a polyester-based, styrene-
It is possible to use a known color toner using an acrylic or other binder. In the present embodiment, the toner is a non-magnetic one-component color, in which a styrene-acrylic resin is used as a base material and a wax is included by a suspension polymerization method so that oil application for preventing offset at the time of fixing is unnecessary. A toner was used.

The transfer material 4 onto which the toner image T has been transferred is heat-fixed by a heat fixing unit 3 having a fixing roller 1 and a pressure roller 2. At this time, the M, C, Y, and K toners are melted by heat. As a result, a predetermined color is obtained, and a full-color image is formed. Here, the fixing roller 1 and the pressure roller 2
As an example, a tetrafluoroethylene-hexafluoropropylene copolymer (FE
P) provided with a release layer was used.

Here, the conditions for fixing will be described in detail.
75 g / m ² plain paper is used as the transfer material 4, the conveyance speed is approximately 120 mm / sec, the outer diameter of each of the fixing roller 1 and the pressing roller 2 is 40 mm, and the rubber hardness is 69 ° (J
IS-A), the fixing roller 1 has a rubber thickness of 1.5 mm, the pressing roller 2 has a rubber thickness of 2 mm, and the FEP thickness of both the fixing roller 1 and the pressing roller 2 is approximately 40 mm. As a result, a nip of approximately 7 mm could be formed. At this time, the temperature of the surface of the fixing roller 1 was adjusted to approximately 180 ° C. by a temperature detecting means (not shown).

When the above-described plain paper (4024-75g paper manufactured by Xerox Corporation) was fixed under the above-described fixing conditions, the glossiness (gloss) of the solid magenta image portion after fixing was approximately 15 °. (The measurement was performed using a 75 ° direction gloss meter manufactured by Nippon Denshoku Co., Ltd.).

Next, instead of plain paper, OHT for a black and white printer is used as a transfer material and coated paper (Darc for high gloss) is used.
Each image was extracted using Laser Cast 95 manufactured by yPaper. At this time, on each piece of paper,
From the relationship between the heat capacity and the required image quality, it has been found that the amount of heat to be applied is insufficient under the above-mentioned fixing conditions for plain paper. When fixing was carried out also in the case of (1), the results as shown in Table 1 below were obtained.

[0032]

[Table 1] In the black-and-white OHT, sufficient transparency can be obtained at 1/3 speed, and this is due to the effect of the wax-containing toner used this time.

As is apparent from the above results, there is a fixing speed suitable for each transfer material.
Problems such as a case where the OHT does not pass through or a glossy paper that produces only the same level of gloss as plain paper occur, and in some cases, a high-temperature offset due to excessive heat supply may occur. . In particular, when a high-temperature offset occurs, the fixing roller 1 and a temperature detecting element that contacts the fixing roller 1 are contaminated with toner, or the transfer material is
And may damage the fixing device 3.

Next, a description will be given of a transfer material identifying means for preventing the above various problems from occurring.

In FIG. 1, reference numeral 8 denotes a reflection type optical sensor (hereinafter referred to as "reflection sensor"), 9 denotes a transmission type optical sensor (hereinafter referred to as "transmission sensor"), 10 denotes a pair of registration rollers,
Reference numeral 11 denotes a computer as control means for controlling fixing conditions based on information corresponding to the type of transfer material identified by the reflection sensor 8 and the transmission sensor 9.

First, an example of the transmission sensor 9 shown in FIG. 2 will be described. In the figure, a transmission sensor 9 includes a light emitting element 12 such as an LED and a light receiving element 13 such as a photodiode.
And reflection mirrors (for example, prisms) 14 and 15 as main components. Since the transmission sensor 9 detects the paper by blocking the optical path of the transfer paper 4, it has high detection sensitivity, and detects the presence or absence of the transfer paper 4 at high speed and reliably.

At this time, when the transfer paper 4 is OHT, light is transmitted and the same state as without paper is obtained. Therefore,
By providing in advance a sensor (not shown) such as a mechanical detection member that moves the lever by paper in advance on the upstream side of the transmission sensor 9, light is transmitted by the transmission sensor 9 even though paper is detected by this sensor. If it is transmitted, it can be determined that it is an OHT.

Next, an example of the reflection sensor shown in FIG. 3 will be described. The reflection sensor 8 irradiates light from a light source 16 such as an LED onto the transfer paper 4 as a reflection surface, and receives the reflected light with a light receiving element 17 such as a photodiode. The incident angle θ ₁ = reflection angle θ ₂ is a specular reflection sensor, θ ₁ ≠ θ
_{The two} are called diffuse reflection sensors. Here, the regular reflection type sensor has a large amount of reflected light received on a smooth surface such as OHT or high gloss paper, and to a certain extent like plain paper.
For the transfer paper 4 having a rough surface, the amount of reflected light received decreases.

On the other hand, the diffuse reflection type sensor hardly receives the reflected light of the light irradiated to the OHT, while the amount of reflected light from high gloss paper or plain paper is almost the same.

The above is summarized in Table 2 below.
become that way.

[0041]

[Table 2] Next, as shown in FIG. 1, the reflection sensor 8 and the transmission sensor 9 move the reflection sensor 8 in the vicinity of the registration roller pair 10 on the upstream side of the transfer path of the transfer paper 4 from the transfer roller 6 to the position far from the registration roller pair 10. The transmission sensor 9 is disposed, and the regular reflection type sensor shown in Table 2 is used as the reflection sensor 8. Then, the transfer paper 4 is identified by the transmission sensor 9, and as a result, if the transfer paper 4 is OHT,
Immediately reduce the transport speed to 1/3 times speed. When an experiment was actually performed, the time required for the deceleration was about 0.5 seconds. That is, the distance between the transfer roller 6 and the transmission sensor 9 may be about 60 mm from the transport speed of the transfer paper 4.

On the other hand, if the detection result of the transmission sensor 9 is not OHT, the reflection sensor 8 continues to discriminate whether it is plain paper or high gloss paper. If the identification result is a high gloss paper, the transport speed is immediately set to 1
Decrease to / 2x speed. This deceleration took about 0.3 seconds. Generally, high gloss paper does not need to be as slow as OHT, so the reflection sensor 8 can be arranged downstream of the transmission sensor 9. In the present embodiment, the distance between the transfer roller 6 and the transmission sensor 9 may be about 30 to 40 mm based on the transport speed of the transfer paper 4.

The above configuration has the following advantages. (1) The transmission sensor 9 is used on the transfer material upstream side of the registration roller pair farther than the registration roller pair 10 to first determine only whether or not the sheet is OHT, so that there is no erroneous detection between plain paper and OHT. Thus, a high-temperature offset state on plain paper can be reliably avoided. (2) The deceleration time can be ensured by disposing the transmission sensor 9 relatively upstream of the transfer roller 6 on the conveyance path of the transfer paper 4 and farther than the reflection sensor 8. (3) The reflection sensor 8 uses a regular reflection type sensor having the highest discrimination ability between plain paper and high gloss paper, and the transmission sensor 9 uses O
After identifying whether the paper is HT or not, plain paper and high-gloss paper are identified, so that O
HT, plain paper, and high gloss paper can be determined very accurately.

In particular, in (1) and (3), by using a combination of a transmission sensor and a regular reflection type sensor, it is possible to cover each other's weak points and to make settings that make the most of their advantages. Becomes <Second Embodiment> Next, a second embodiment of the present invention will be described.

In the first embodiment, if the transfer paper 4 vibrates or undulates during conveyance, the regular reflection type sensor 8 has difficulty in determining whether the paper is high gloss paper or plain paper. This is because the amount of light varies in the parallel shift, and in
This is for approaching the diffuse reflection type sensor. That is, the transfer paper 4
When the reflection position of the transfer paper 4 which reflects the light from the light source 16 of the reflection sensor 8 by vibrating or waving becomes closer to the reflection sensor 8 than the position shown in FIG. When the position is inclined with respect to the reflection sensor 8 from the position in FIG. 3, the received light substantially approaches the diffuse reflection type sensor.

The present embodiment is to solve this point. This will be specifically described with reference to FIGS.

In FIG. 4, the transfer paper 4 is a pair of registration rollers 1
0, that is, the registration roller pair 10
5 shows an example in which the transfer paper 4 is identified by the reflection sensor 8 on the upstream side near the registration roller pair 10 (within several mm) in a state where the transfer paper 4 is held between the nips formed by the transfer paper 4. In this state, when the transfer paper 4 enters the registration roller pair 10 and undulates, the detection level of the light receiving element 17 that receives light from the light source 16 becomes unstable, but the registration roller pair 10 is rotated. When the transfer paper 4 is pulled, an extremely stable detection level can be obtained.

On the other hand, in FIG. 5, while the transfer paper 4 is restrained by the pair of registration rollers 10, the pair of registration rollers 1
An example is shown in which the transfer paper 4 is identified by the reflection sensor 8 having the light source 16 and the light receiving element 17 on the downstream side near zero. This state is particularly caused by the registration roller pair 10.
Is most suitable for a system that controls the timing of the leading edge of the paper such that it temporarily stops with the leading edge of the paper pinched by several mm. Because
In this state, since the leading end detection portion of the transfer paper 4 has a stiffness and does not undulate, the detection can be performed very stably.

FIG. 6 shows an example in which the transfer paper 4 is determined from the registration roller pair 10 while the transfer paper 4 is restrained by the registration roller pair 10. This is actually performed as shown in FIG.
This is a method in which, when a roller having rubber or the like divided in the longitudinal direction is used, detection is performed by aiming at a gap between the rubber rollers. Since the gap is small, the degree of freedom in design is narrow, but the binding force of the transfer paper is the best. Of course, in these arrangements, the distance between the registration roller pair 10 and the transfer roller 6 is further limited, and the transmission sensor 9 which is the OHT detection sensor in FIG. It is good to arrange on the upstream side.

In each of the above embodiments, the apparatus using the intermediate transfer belt 5 has been described. However, it is needless to say that other transfer methods can be similarly applied without any problem.

Further, in the above-described embodiment, the setting of the fixing condition of the fixing device 3 is described by changing the transport speed. However, the setting may be performed by changing the fixing temperature.

[0052]

As described above, according to the present invention,
The transmissive optical sensor identifies whether the transfer material is a light transmissive sheet, and the reflective optical sensor identifies whether the transfer material is glossy paper. By providing the transfer material upstream of the optical sensor on the conveyance path of the transfer material, switching when the light transmitting sheet is identified can be performed smoothly, and the transfer material can be identified with high accuracy.

Further, according to another aspect of the invention, by providing the reflection type optical sensor near the pair of registration rollers, it is possible to more accurately discriminate between glossy paper and plain paper.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing the transmission optical sensor according to the first embodiment;

FIG. 3 is a schematic configuration diagram showing the reflection type optical sensor of FIG. 1;

FIG. 4 is a schematic configuration diagram showing a reflection type optical sensor for explaining a second embodiment of the present invention.

FIG. 5 is a schematic sectional view illustrating a second embodiment.

FIG. 6 is a schematic cross-sectional view illustrating a second embodiment.

FIG. 7 is a schematic perspective view illustrating a second embodiment.

FIG. 8 is a schematic sectional view showing a conventional fixing device.

FIG. 9 is an enlarged sectional view showing a main part of the fixing device of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 fixing means (fixing device) 4 transfer material 8 reflection type optical sensor 9 transmission type optical sensor 10 registration roller pair 11 control means (computer) 16 LED 17 photodiode

Claims (5)

[Claims] 1. An image forming apparatus having a fixing unit for fixing a toner image transferred onto a transfer material, wherein the image forming apparatus is disposed at a predetermined position upstream of a transfer path of the transfer material from a transfer position of the toner image to the transfer material. A transmission-type optical sensor for identifying whether or not the transfer material is a light-transmitting sheet; and a transmission-type optical sensor disposed downstream of the transmission-type optical sensor from the transmission-type optical sensor and upstream of the transfer position. A reflection-type optical sensor that determines whether or not the material is glossy paper; and if the transfer material is not a light-transmitting sheet, the reflection-type optical sensor determines whether or not the transfer material is glossy paper. And a control unit for setting a fixing condition of the fixing unit for fixing the toner image on the transfer material based on the identification result. 2. The image forming apparatus according to claim 1, wherein the reflection type optical sensor is disposed near a pair of registration rollers upstream of the transfer position. 3. The image forming apparatus according to claim 1, wherein the reflection type optical sensor is a regular reflection type optical sensor. 4. The image forming apparatus according to claim 1, wherein the control unit sets a transfer speed of the transfer material as the fixing condition. 5. The image forming apparatus according to claim 1, wherein the control unit sets a fixing temperature of the fixing unit as the fixing condition.